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United States Patent |
5,113,460
|
Hakoun
,   et al.
|
May 12, 1992
|
Optical device having an integrated optical component, and method of
manufacture
Abstract
The device includes a first jointing component for joining two fibers to
two integrated optic outlet waveguides in the glass substrate, these two
fibers are mounted touching one another to constitute a sheet which is
itself bonded between two plates of glass, and the spacing of the two
corresponding waveguides is equal to the diameter of the fibers, said
first jointing component together with its fibers and a second jointing
component together with another fiber at the inlet waveguide being bonded
against said substrate.
Inventors:
|
Hakoun; Roland (Domont, FR);
Tanguy; Eric (Paris, FR)
|
Assignee:
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Alcatel Fibres Optiques (Cedex, FR)
|
Appl. No.:
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688792 |
Filed:
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April 22, 1991 |
Foreign Application Priority Data
Current U.S. Class: |
385/39; 385/88 |
Intern'l Class: |
G02B 006/00; G02B 006/36 |
Field of Search: |
350/96.15,96.16,96.20-96.22
|
References Cited
U.S. Patent Documents
4647147 | Mar., 1987 | Pikulski et al. | 350/96.
|
4906068 | Mar., 1990 | Olson et al. | 350/96.
|
4948219 | Aug., 1990 | Seino et al. | 350/96.
|
Foreign Patent Documents |
0283301 | Sep., 1988 | EP.
| |
Other References
Patent Abstracts of Japan, vol. 14, No. 158 (P-1027)[4101], Mar. 27, 1990;
& JP-A-2 15 204 (NIT), Jan. 18, 1990.
Patent Abstracts of Japan, vol. 6, No. 104 (P-122)[982], Jun. 15, 1982; &
JP-A-57 35 820 (Shimazu Seisakusho) Feb. 26, 1982.
|
Primary Examiner: Ullah; Akm E.
Attorney, Agent or Firm: Sughrue, Mion, Zinn, Macpeak & Seas
Claims
We claim:
1. An optical device including an integrated optical component having a
substantially rectangular glass substrate including integrated optical
waveguides, and defining between them a coupler having first ends of said
waveguides on one of the end faces of the substrate and at least one
second end of the waveguides on the opposite end face of the substrate,
and further including a first jointing component for joining first optical
fibers to first ends of the waveguides, and a second jointing component
for joining a second optical fiber to each second end, each of the
jointing components being bonded to said glass plates holding said first
fibers therebetween, with the spacing of said first fibers being
substantially equal to the spacing of the first ends of the waveguides,
wherein the spacing of the waveguides, at least at said first ends, is
substantially equal to the diameter of said first fibers when covered,
wherein said covered first fibers form a sheet of touching fibers in said
first jointing component, wherein the inside faces of the plates of said
first jointing component are plane, wherein said optical device further
includes a support piece having a central flat on which said substrate is
mounted, and two ends on which said optical fibers are supported and
bonded beyond said first and second jointing components, and said second
jointing component is constituted by a slab or tube of glass having a
channel passing therethrough in which the stripped end of the single
second fiber is threaded and held, and is bonded against the substrate
during alignment of said second fiber with the corresponding second end of
the waveguides.
2. An optical device according to claim 1, wherein the ends of the support
piece have respective cavities for receiving the adhesive for bonding the
fibers in respective zones that are several millimeters across.
3. An optical device according to claim 1, wherein said support piece has
two notches on either side of said central flat for receiving said first
and second jointing components without making contact therewith.
4. An optical device according to claim 1, wherein said second jointing
component is made in the same manner as the first jointing component to
hold each second fiber by means of its covering.
5. A method of manufacturing the optical device including an integrated
optical component having a substantially rectangular glass substrate
including integrated optical waveguides, and defining between them a
coupler having first ends of said waveguides on one of the end faces of
the substrate and at least one second end of the waveguides on the
opposite end face of the substrate, and further including a first jointing
component for joining first optical fibers to the first ends of the
waveguides, and a second jointing component for joining a second optical
fiber to each second end, each of the jointing components being bonded to
said substrate, said first jointing component being constituted by two
glass plates holding said first fibers therebetween, with the spacing of
said first fibers being substantially equal to the spacing of the first
ends of the waveguides, wherein the spacing of the waveguides, at least at
said first ends, is substantially equal to the diameter of said first
fibers when covered, wherein said covered first fibers form a sheet of
touching fibers in said first jointing component, and the inside faces of
the plates of said first jointing component are plane, said method
comprising:
forming said waveguides on said glass substrate with the spacing of said
first ends of the waveguides being equal to the diameter of said first
optical fibers when covered;
assembling the covered first fibers by means of an adhesive so that they
touch one another to form a sheet;
bonding said two glass plates on opposite faces of the sheet by means of
adhesive spread over an internal bonding zone which excludes the end of
the sheet that is substantially flush with each of the interface edges
constituting interfaces with the substrate, and excluding the portion
adjacent to the interface edges,
and placing a wedge fiber together with said sheets between said plates,
said wedge fiber being offset from the sheet and having its end set back
from the interface edges of the plates, and being free from any adhesive.
6. A method according to claim 5, further comprising in cleaving the end of
the made-up sheet before it is mounted and bonded between said plates,
thereby causing it to present a new end which is rectified and free from
adhesive.
7. A method according to claim 6, further comprising in prepositioning the
first and second jointing components against the substrate with their
fibers in approximate alignment with the ends of the waveguides, and
adjusting their positions accurately by monitoring the maximum flux
flowing through said fibers and said waveguides, prior to bonding said
first and second jointing components to said substrate.
Description
The present invention relates to optical devices such as couplers of the
type including an integrated optical component on which optical fibers are
terminated.
BACKGROUND OF THE INVENTION
In conventional manner, the technique of "optical integration" makes it
possible to create waveguides in a dielectric substrate, generally glass,
by locally increasing the refractive index of the glass. These waveguides
are made by the method of diffusing ions into the substrate or by the
method of depositing layers having a refractive index greater than that of
the substrate.
Such integrated optical components are being used more and more in the
fields of transmission by means of optical fibers. They are made small in
size with their waveguides at very small spacing, and they are suitable
for making up various different coupler structures. These different
coupler structures include, in particular, Y-couplers having a common
branch referred to as the inlet and connected to two "outlet" branches
which are at a very small junction angle to each other. These structures
also include, for example, proximity couplers having two waveguides which
are very close together, at least in a central portion, or other types of
coupler which are also known per se.
The main problem encountered in industrial use of integrated optical
components is the accuracy with which optical fibers need to be aligned
relative to the substrate waveguides. This accuracy is of the order of one
micron or less. It is difficult to obtain because of the lack of strength
of optical fibers. It is all the more difficult to obtain because the ends
of the fibers are close together, leaving little or no freedom for final
adjustment by micromanipulation of the fibers.
Thus, it is common practice for integrated optical waveguides to be formed
on the glass substrate with their ends far enough apart to enable
individual fibers facing the waveguides to be manipulated and to make it
easy to bond them to the substrate.
In addition, in order to ensure good mechanical behavior of the fibers
while they are being put into position facing the waveguides, and
optionally being subjected to final adjustment by micro-manipulation prior
to being bonded to the substrate, integrated optical components are known,
in particular from the documents FR-A-2 574 950 and FR-A-2 612 302 in
which the glass substrate includes not only the waveguides that are formed
therein, but also grooves for positioning the fibers. These grooves and
the waveguides are aligned as accurately as possible. According to those
documents, the grooves are integrally molded in the substrate and the
waveguides are formed subsequently on the substrate. This method of
manufacture is lengthy and difficult. It requires adjustment by
micro-manipulation for end-to-end jointing of fiber after fiber facing the
various waveguides.
Document EP-A-0 283 301 also describes a component for end-to-end jointing
of fibers to waveguides, the component being constituted by two facing
groove plates in which the fibers are held. Each fiber is stripped and has
one of its ends lying in the front face plane of the component. This end
is fixed to the end of one of the waveguides, by the components being
fixed to the substrate. In a variant, the covered fibers are held in the
end-to-end jointing component each having a stripped end projecting a
little from the component and being bonded to the end of a waveguide when
the component is fixed to the substrate.
An object of the present invention is to make it simpler and cheaper to
obtain optical devices having integrated optical components with fibers
joined end-on thereto, and in particular providing considerably improved
mechanical strength in traction.
SUMMARY OF THE INVENTION
The present invention provides an optical device including an integrated
optical component having a substantially rectangular glass substrate
including integrated optical waveguides, and defining between them a
coupler having first ends of said waveguides on one of the end faces of
the substrate and at least one second end of the waveguides on the
opposite end face of the substrate, and further including a first jointing
component for joining first optical fibers to be first ends of the
waveguides, and a second jointing component for joining a second optical
fiber to each second end, each of the jointing components being bonded to
said substrate, said first jointing component being constituted by two
glass plates holding said first fibers therebetween, with the spacing of
said first fibers being substantially equal to the spacing of the first
ends of the waveguides, wherein the spacing of the waveguides, at least at
said first ends, is substantially equal to the diameter of said first
fibers when covered, and wherein said covered first fibers form a sheet of
touching fibers in said first jointing component.
In particular, the inside faces of the plates are plane. Further, the
second end-to-end jointing component is identical to the first or is
constituted by a part which is pierced by a channel into which the
stripped end of the second fiber is inserted and fixed.
The present invention also provides a method of manufacturing the optical
device, wherein the method consists in:
forming said waveguides on said glass substrate with the spacing of said
first ends of the waveguides being equal to the diameter of first fibers
when covered;
assembling the covered first fibers by means of an adhesive so that they
touch one another to form a sheet; and
bonding two glass plates on opposite faces of the sheet by means of
adhesive spread over an internal bonding zone which excludes the end of
the sheet that is substantially flush with each of the interface edges
constituting interfaces with the substrate, and excluding the portion
adjacent to the interface edges.
BRIEF DESCRIPTION OF THE DRAWINGS
An embodiment of the invention is described by way of example with
reference to the accompanying drawings, in which:
FIG. 1 is a diagrammatic plan view of a device of the invention;
FIG. 2 is an elevation view of the FIG. 1 device;
FIG. 3 is a plan view on a larger scale of one of the components of the
FIG. 1 device; and
FIG. 4 is a section view through said component on line IV--IV of FIG. 3.
DETAILED DESCRIPTION
With reference to FIGS. 1 and/or 2, it can be seen that an optical device
of the invention or "optical coupler" essentially comprises:
a glass substrate 1 having integrated optical waveguides therein given
overall reference 2 and constituting, in the example shown, a Y-coupler
having a common branch 3 referred to as the "inlet" waveguide, and a set
of two other branches 4A, 4B connected thereto to constitute "outlet"
waveguides, with the ends of these waveguides on either side of the
junction therebetween occupying respective ones of the small end faces of
the substrate 1;
a first component 5 for assembling and holding two optical fibers 6A and
6B, the components being held against the small end face of the substrate
containing the outlet waveguides 4A and 4B, and being bonded to the
substrate 1 with its two fibers being in end-to-end alignment with
respective ones of these two outlet waveguides;
a second component 7 for holding another optical fiber 8, which component
is applied against the other small end face of the substrate, with the
fiber 8 in the component being in end-to-end alignment with the inlet
waveguide 3; and
a support piece 9 which is preferably made of metal, and preferably of
Invar, with the substrate 1 being mounted thereon and bonded thereto
together with its end fiber-holding components 5 and 7, and on which
fibers are bonded at opposite ends of the substrate and its end components
in zones 11 and 12 near the ends of the support piece, which zones are a
few millimeters across.
The outlet waveguides 4A and 4B are at a very small angle to each other on
the glass substrate 1, which angle is of the order of one degree to a few
degrees, where they join the inlet waveguide. In addition, they are also
formed so that their respective ends terminate on the small end face of
the substrate at a mutual spacing equal to the diameter of the covered
optical fibers connected thereto. For the fibers 6A and 6B that have a 250
micron diameter covering, this spacing is 250 microns.
The first component 5 together with its fibers 6A and 6B serves to hold
these two fibers assembled together in a sheet. The way it is implemented
can be seen with reference to FIGS. 1 and 2, and more particularly with
reference to FIG. 3 and/or FIG. 4.
To make up the sheet designated 6, the two covered fibers 6A and 6B are
initially bonded side by side by means of a fillet of a resin that
polymerizes under ultraviolet radiation and deposited between the fibers
on their resin coverings. The end of the sheet formed in this way is
preferably cut by means of an appropriate cutting tool, so as to obtain a
new end which is very clean and which is free in particular from any of
the adhesive at the ends of the fibers.
This sheet is then bonded between two plates of glass 5A and 5B using the
same type of adhesive as before. This operation is performed while taking
care to ensure that the end of the sheet is exactly flush with the two
facing edges of the plates defining the interface edges of the connection,
and that they receive no adhesive. This end may optionally be rectified
and is assumed below to be rectified. As shown in FIG. 3, the rectified
end of the sheet 6 is flush at 15 with the above-mentioned connection
interface edges, and sheet adhesive between the plates is spread between
the plates on either side of the sheet over a wide zone 17 which excludes
the portion adjacent to the interface edges such as the rectified end of
the sheet 6.
For the purpose of making this assembly, an additional fiber 16 referred to
as a "wedge" fiber is mounted independently to one side of the fibers in
the sheet 6 and like them is bonded between the plates of glass. The end
16A of the wedge fiber 16 is set back a little from the interface edges of
the plate and is free from adhesive. This wedge fiber 16 is preferably
bonded to one of the plates before the sheet 6 is bonded thereto.
In FIGS. 1 and 2, the second component 7 serves to hold the single fiber 8
end-to-end with the inlet waveguide 3. It is constituted by a small slab
or tube referred to as a ferrule and pierced with a channel which is not
referenced. The end 8A of the fiber 8 is stripped and is threaded through
and then bonded to the ferrule with its end lying flush with the end face
that serves as the interface, and being free from adhesive.
In a variant, this second component could be constituted like the component
5, with the fiber 8 replacing the above-mentioned sheet 6 between two
sheets of glass where it would then remain covered with its resin
covering.
The two components are mounted to respective ends of the substrate by means
of clamps mounted on micrometer displacement means enabling the final
position adjustment of the fibers to be performed with the required
accuracy after the fibers have been installed approximately in alignment
together with the respective waveguides. By monitoring the light flux
coming from the fiber 8 and travelling in the fibers 6A and 6B after
passing through the waveguides 2, it is possible to detect the optimum
coupling and thus the optimum positioning. Once this adjustment has been
achieved, the components 5 and 7 are bonded to the substrate by means of a
polymerizable adhesive, as shown at 18 and 19, with the adhesive extending
between their contacting faces and over the margins of the substrate 1.
The assembly constituted by the integrated optical component 1 and the
components 5 and 7 including their fibers is then mounted and bonded on
the support piece 9 which is appropriately machined prior thereto.
The central portion 9A of the support piece 9 has a flat on which the glass
substrate 1 rests. The substrate is preferably bonded to the flat in order
to avoid any risk of subsequent vibration. Also advantageously, as shown
in FIG. 2, the substrate is mounted with its face in which the wave-guides
2 are formed applied to the flat so as to prevent the jointing components
5 and 7 projecting above the resulting coupler.
On either side of the central plate 9A, the support piece 9 has two
respective notches 9B and 9C in which the jointing components 5 and 7 are
received without making contact. The two ends 9D and 9E of the support
piece 9 are rectified to a slightly different height from the central flat
9A so as to define support surfaces for the two fibers 6A and 6B in the
sheet and for the fiber 8. Each of these ends has a central cavity 9F
which receives adhesive for bonding to the corresponding fiber or sheet of
fibers. This adhesive penetrates into the cavity and forms a dome over the
fiber(s). It holds the fibers captive in resin that has set and ensures
that the fibers are well held at opposite ends of the substrate and beyond
the jointing components 5 and 7.
The support piece 9 also has intermediate shoulder portions such as 9G
between each of its ends and the adjacent notch for receiving the jointing
component 5 or 7, for the purposes of good mechanical strength.
Implementation of the resulting coupler is greatly simplified and thus made
cheap. It also has very good mechanical strength in traction and under
varying environmental conditions, and it has very low losses in the
connection formed between the fibers and the waveguides.
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